1. Field of the Invention
The present invention relates to a technique for estimating a curve's radius of a road on which a vehicle shall run, and more particularly to a technique for improving accuracy of such estimation.
2. Description of the Related Art
There is an example of a conventional technique for estimating the curve's radius (a radius of curvature) of the road to be traveled by the vehicle (see Japanese Laid-Open Patent Application No. 2001-328451).
In this conventional technique, a first curve's radius representing a course of the vehicle is calculated by alternatively using a steering angle of a steering wheel handled by a driver of the vehicle and a yaw rate of it. Also, a second curve's radius representing the course of the vehicle is calculated by using a position of a stationary object (such as a fixedly-installed reflecting mirror) located in the front of the vehicle. Further, a third curve's radius representing the course of the vehicle is calculated by averaging the above two types of calculated curve's radius.